Chorismate biosynthesis involves the last few steps in the common pathway for the production of the aromatic amino acids phenylalanine, tyrosine and tryptophan. The first step in chorismate biosyntheis is performed by 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase, also called DAHP synthetase. Two differentially expressed forms of this enzyme are present in plant tissues and are important regulators of the flux to aromatic amino acid biosynthesis. DAHP synthetase has been described for tomato, tobacco, potato, alfalfa and Arabidopsis thaliana (Wang, Y., et al. (1991) Plant Physiol. 97:847-848; Gorlach, J., et al. (1993) Plant Mol Biol 23:697-706; Dyer, et al. (1990) J. Biol. Chem. 265:1608-1614; Keith, B., et al. (1991) Proc. Natl. Acad. Sci. USA 88:8821-8825; Zhao, J., and Herrmann, K. M. (1993) Plant Physiol. 100:1075-1076).
Manipulating either the amount or activity of these enzymes would afford manipulation of the ratio of aromatic to non-aromatic amino acids in plants, including corn, rice, sorghum, soybean and wheat. This enzyme should also be useful for high throughput screening of compounds suitable for use as herbicides.